Hi,
If it is 80F outside and inside, time to check the performance of your rooftop A/C unit. If it is taking in 80F air, then the output should be 18 - 22F cooler, or around 60F.
Getting a inside/outside thermometer can monitor the system. Just use the outside probe to measure the air out of the ductwork, and see what it is doing. I put one out my side window for a while, and had it sitting next to my dinette table, and then I can tell how warm it is outside. Later I installed it in my bedroom, and secured the outside temp sensor under the RV, in the shade, so I can get up and see what it is like outside. When driving, I guess it is picking up the engine heat, as I know that the max temp outside was not 128F!
A portable A/C with two hoses will take in outside air, heat it, then blow it back outside. It will work, but the A/C and all it's noise will be in the room with you. As explained a couple of days ago to someone else, a single pipe portable A/C takes cooled and dry inside air, at about 150 CFM and blows it outside to cool the portable A/C, thus a 300 square foot RV with 8' ceilings will get all the air blown outside in about 16 minutes, bringing in new unfiltered moist outside air to replace all that is consumed by the portable A/C unit. So it will be noisy and hot with a single pipe unit.
Your roof top A/C, the motor sits outside (under a cover) so it's heat and noise is outside, not warming the air inside the RV. The compressor likewise is outside, any heat it gives off is outside. The outdoor coil also uses outside air to cool it. So they are much more efficient than a portable A/C with all that noisy stuff right next to your bed or dinette table.
Penguin is a good brand name from what I have heard. Check by removing the inside cover of your rear roof vent. In mine, I found 12 volt wiring from the panel that was live, and I hooked up a Fantastic fan in the bedroom, bath and kitchen. I did not find 120 volt wires pre-installed at the factory, but it might be up there, I was not looking for it. Yours might be different anyway!
If you find the wiring, and have some strong friends, especially one with a pickup and 6' or 8' ladder, putting the ladder into the pickup gives you a platform that is 5' off the ground to work from. You can practically hand the A/C from the pickup to the rooftop, then put it on a thick blanket, while you work on installing it. Several layers of the blanket will keep it from poking expensive holes into the roof surface. I think that the A/C will range from 60 to 100 pounds, check the website for exact details.
The opening is basically the same with all manufactures. 14" square, and normally it is really 14-1/4". You remove the old vent, sealants, and clean the roof. Put down the gasket, set the A/C into place, connect 4 bolts to the inside surface mount, and then snug those bolts to tighten the gasket between the A/C and roof. No sealant is used, so that the gasket will be easy to replace in about 15 years. Snug the bolts again in about 6 months and at every 2 years after that.
9,000 Btu's should be a quiet unit, and also allow the front unit to cycle off from time to time, and be low enough wattage that if you are at a 30 amp site, the front 14 amp A/C and new rear 9 amp A/C will both run without a problem. However many report running two A/C units on a 30 amp site without problems, so you might find that the smallest stock A/C is a 13,500 Btu model.
If your current A/C is only cooling the air by about 10F or 14F, then it is probably low on Freon, and needs to be recharged or replaced. It can take over 4 hours to fix a leak, that can cost upwards of $500, and you can buy a new unit with a full warranty for that kind of money.
Good luck on your decision, and happy camping!
Fred.
